/Engine/Source/Runtime/Engine/Classes/Materials/Material.h
Returns all the Guids related to this material. For material instances, this includes the parent hierarchy. Used for versioning as parent changes don't update the child instance Guids.
virtual void GetLightingGuidChain ( bool bIncludeTextures, [TArray](API\Runtime\Core\Containers\TArray)< [FGuid](API\Runtime\Core\Misc\FGuid) > & OutGuids ) const